Process for preparing laminar articles from a mixture of a polyolefin and ethylene/vinyl alcohol copolymers

ABSTRACT

A process for preparing a laminar article with multiple thin, overlapping layers, includes preparing a melted heterogeneous blend of a polyolefin, an ethylene-vinyl alcohol copolymer, and a compatibilizer having a specified level of grafted cyclic anhydride groups; extending the body of the melt; and cooling the extended body to below the melting point of the polyolefin.

This is a division of application Ser. No. 07/351,921, filed May 15,1989, now U.S. Pat. No. 4,971,864.

BACKGROUND OF THE INVENTION

This invention relates to laminar blends of polyolefins andethylene-vinyl alcohol copolymers which have superior barrier andphysical properties.

Containers and films which are blends or laminates of polyolefins andethylene-vinyl alcohol copolymers have been the subject of severalinvestigations because this combination of polymers has the potentialfor providing high resistance to permeation by water, oxygen, andhydrocarbons.

U.S. Pat. No. 3,975,463 discloses a resinous composition of (a) 30 to98% by weight of a crystalline polyolefin, (b) 2 to 70% by weight of asaponified product of an ethylene vinyl acetate copolymer, and (c) 0.5to 15 parts by weight of a thermoplastic polymer containing a carbonylgroup in the main or side chain, and a molded structure formedtherefrom, which has a specific multilayer structure and a high gaspermeation resistance. The thermoplastic polymer (c) can be a copolymerof maleic anhydride or an acrylic acid grafted polyethylene.

European Patent Application 15556 discloses a process for manufacturinglaminar articles by forming heterogeneous melts of a combination of apolyolefin and a second polymer with an alkylcarboxyl substitutedpolyolefin as a compatibilizing material, and the laminar articles soformed. The second polymer can be poly(ethylene-co-vinyl alcohol), andthe compatibilizing material can be obtained by melt-grafting fumaricacid onto polyethylene. In particular, a grafted material is disclosedwhich was grafted with about 0.9 weight percent fumaric acid; the ratioof polyolefin:second polymer:compatibilizer can be 65:30:5.

A study of barrier materials prepared following the teachings of U.S.Pat. No. 3,975,463 and European Patent Application 15556 revealed thatthe laminar structures of European Patent Application 15556 are capableof providing better barriers than the composites of U.S. Pat. 3,975,463.However, the laminar structures prepared following the teaching ofEuropean Patent Application 15556 (particularly Examples 12 and 13) werefound to exhibit significant variation in resistance to permeation byhydrocarbons and oxygen and in mechanical strength. Such variations areundesirable in laminar structures which are to be used in demandingapplications such as containers for hydrocarbon fuels and packaging forperishable foodstuffs. Thus a need exists to provide polyolefin/ethylenevinyl alcohol copolymer laminar structures which will consistentlyprovide optimum barrier properties and mechanical strength.

SUMMARY OF THE INVENTION

Laminar articles prepared from the following ingredients in the amountsspecified consistently exhibit outstanding barrier properties towardwater, oxygen and hydrocarbon solvents and have good mechanicalproperties.

Specifically, the present invention provides a laminar articleconsisting essentially of a laminar article consisting essentially of acombination of

(a) a polyolefin;

(b) an ethylene-vinyl alcohol copolymer containing about 20-60% byweight of ethylene units, said copolymer having a melting point at leastabout 5° C. higher than said polyolefin; and,

(c) a compatibilizer comprising a polyolefin backbone having graftedthereon cyclic anhydride moieties in an amount such that the carbonylcontent of the compatibilizer is about 0.3-4.0% by weight, saidpolyolefin backbone prior to grafting being miscible with saidpolyolefin (a);

wherein the ethylene-vinyl alcohol copolymer is present within thepolyolefin as multiple, thin, substantially parallel, overlappinglayers;

the quantity of polyolefin (a) being 0 to about 97.9% by weight, thequantity of ethylene-vinyl alcohol copolymer (b) being about 2-20% byweight, both based on the total weight of (a), (b), and (c), and thequantity of compatibilizer (c) being such that the ratio of the weightof carbonyl groups in the compatibilizer to the weight of ethylene-vinylalcohol copolymer (b) is about 0.0014:1.0 to about 0.006:1.0.

The present invention further provides a process for manufacturing alaminar, shaped article of polymeric material comprising the steps of:

(a) establishing a melted, heterogeneous blend of polyolefin, anethylene-vinyl alcohol copolymer containing about 20-60% by weight ofethylene units and having a melting point at least about 5° C. higherthan the polyolefin, and a compatibilizer comprising a polyolefinbackbone having grafted thereon cyclic anhydride moieties, in an amountsuch that the carbonyl content of the compatibilizer is about 0.3-4.0%by weight, said polyolefin backbone prior to grafting being misciblewith said polyolefin;

(b) extending a body of the melt; and

(c) cooling the extended body to below the melting point of thepolyolefin.

DETAILED DESCRIPTION OF THE INVENTION

The polyolefin (a) used in preparing the laminar articles of thisinvention includes polyethylene, polypropylene, polybutylene, andrelated copolymers. Polyethylene is preferred and may be high, medium,or low density material.

Component (b) is an ethylene-vinyl alcohol copolymer containing about 20to about 60% by weight of ethylene, which copolymer is furthercharacterized by having a melting point at least about 5° C. greaterthan polyolefin (a). More preferably, the ethylene-vinyl alcoholcopolymer will have a melting point at least about 10° C. greater thanpolyolefin (a). For higher melting polyolefins, the requirement that thecopolymer be higher melting than the polyolefin limits the amount ofethylene which may be present in the ethylene-vinyl alcohol copolymer toless than 60% by weight. For example, when using polypropylene having amelting point of about 168° C., ethylene-vinyl alcohol containinggreater than about 35% by weight of ethylene will not be useful becausesuch copolymers have melting points which are around or below 168° C. Asis well known to those skilled in the art, the required ethylene-vinylalcohol copolymers are prepared by saponification of ethylene-vinylacetate copolymers. For use in the present invention, the degree ofsaponification should be greater than about 95% and preferably at least99 %. Typically these copolymers have number average molecular weightsof about 20,000 to 80,000, but their molecular weight is not directlycritical to this invention. As will be described in detail hereinafter,it is preferred that the melt viscosity of the ethylene-vinyl alcoholcopolymer be 1.1 to 3.5 times greater than the melt viscosity of thepolyolefin at the temperature at which the laminar articles are formed.Therefore, only to the extent that molecular weight is related to meltviscosity is the molecular weight of the ethylene-vinyl alcoholcopolymer significant.

Component (c), the compatibilizer, is a graft polymer with a polyolefinbackbone onto which cyclic anhydride moieties, derived from maleicanhydride, for example, have been grafted. The compatibilizer serves toadhere adjacent layers of polyolefin and ethylene-vinyl alcoholcopolymer to one another. It is important in preparing the laminararticles of this invention that the olefin polymer serving as thebackbone of the graft polymer be miscible, prior to grafting, withpolyolefin (a). In effect, this restriction essentially requires thatthe compatibilizer be prepared from a polyethylene backbone whencomponent (a) is polyethylene or from a polypropylene backbone whencomponent (a) is polypropylene. However, it is recognized that randomcopolymers containing only very small amounts of olefin comonomer areprobably miscible with homopolymers based on the major component of suchrandom copolymers. For instance, it is believed that randomethylene/propylene copolymers containing up to about 8 mole % ethyleneare miscible with polypropylene homopolymer. As will be shownhereinafter in the examples, a variety of polymers having either graftedor copolymerized cyclic anhydride moieties have been tested ascompatibilizers. Even such closely related polymer backbones asethylene-propylene-hexadiene terpolymers having maleic anhydridemoieties grafted thereon are less effective when polyolefin (a) ispolyethylene or polypropylene than are compatibilizers based on polymerbackbones which correspond to polyolefin (a). The compatibilizer isfurther characterized in that it contains grafted cyclic anhydridemoieties in an amount such that carbonyl content of the compatibilizeris about 0.3-4.0% by weight. Such grafts can be prepared with anhydridecontents ranging from essentially 0 to about 8% anhydride, expressed asweight percent maleic anhydride. A polymer containing 8% anhydridecontains about 163 meq CO per 100 g polymer. A useful range of anhydridecontent, however, is about 0.5 to about 5.5% anhydride, expressed asweight percent maleic anhydride, or a carbonyl content of about 0.3 toabout 4%. For example, maleic anhydride has a formula weight of 98.06and contains 2 C═O groups, formula weight 28.01. Thus a compatibilizercontaining 1 weight % anhydride has a carbonyl content of 0.57%. Thecarbonyl content of the compatibilizer can be readily determined bymeasuring the intensity of the anhydride carbonyl peak in the infra-redspectrum of the compatibilizer and comparing the magnitude of this peakwith the magnitude of the same peak in the spectra of polymerscontaining known amounts of the grafted anhydride.

The required compatibilizers can be prepared by procedures such as thosedescribed in U.S. Pat. Nos. 4,026,967 and 4,612,155, the disclosures ofwhich are incorporated herein by reference. While numerous compounds canbe used as graft monomers, maleic anhydride is preferred. Less preferredgraft monomers include mono-esters of maleic acid, maleic acid andfumaric acid, which monomers are believed to be largely converted tocyclic anhydride moieties at the high temperatures encountered duringthe grafting reaction. Also suitable are other cyclic anhydridescontaining carbon-carbon unsaturation such as dodecenyl succinicanhydride, 5-norbornene-2,3-anhydride, and3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride.

In preparing the laminar articles of this invention, the ethylene-vinylalcohol copolymer, which provides the discontinuous phase, is used inamounts of about 2-20% by weight, preferably about 4-15% by weight,based on the total weight of components (a), (b) and (c). Articlescontaining less than about 2% by weight of copolymer generally do notexhibit sufficient improvement in barrier properties toward oxygen orhydrocarbons to be useful commercially. Articles containing greater thanabout 20% by weight of ethylene-vinyl alcohol copolymer exhibitvariations in mechanical strength of such magnitude that the articlesare unreliable for many applications.

The amount of compatibilizer required to prepare the laminar articles ofthis invention is a function of (i) the concentration of ethylene-vinylalcohol copolymer in the article and (ii) the concentration of graftedcyclic anhydride moieties in the compatibilizer expressed in terms ofthe carbonyl content. As previously indicated, the compatibilizer shouldbe used in amounts such that the weight ratio of carbonyl groups in thecompatibilizer to the amount of ethylene-vinyl alcohol copolymer used isabout 0:0014:1.0 to about 0.006:1.0. For example, if one were preparinga laminar article containing 10% by weight ethylene-vinyl alcoholcopolymer and using as a compatibilizer polyethylene having graftedthereon about 1% by weight of maleic anhydride moieties (correspondingto a carbonyl content of 0.5% by weight), then one could use from2.6-10.5% by weight of compatibilizer. Weight ratios of about 0.002:1.0to about 0.004:1.0 are preferred. In the hypothetical example justpresented, these preferred ratios would correspond to 3.5% to 7.0% byweight.

The amount of polyolefin component(a) used in the articles of thisinvention is clearly 100% by weight less the sum of the percentages ofcomponents (b) and (c) (not counting any additional minor amounts ofconventional additives, fillers, etc., which may be used). It ispreferable that the concentration of polyolefin not be less than 60% byweight and more preferable that it not be less than 70% by weight basedon the total weight of the three components.

The articles of the present invention are prepared substantially by theprocess described in U.S. Pat. No. 4,410,482, which is incorporatedherein by reference. The laminated articles are preferably made bymixing together particles of the polyolefin, particles of theethylene-vinyl alcohol copolymer and particles of the compatibilizer,heating the mixture to yield a heterogeneous melt of material andforming the melt in a way which results in extending the melt to yieldmultiple elongated discontinuous polymer domains consisting of theethylene-vinyl alcohol copolymer within a continuous domain ofpolyolefin. As used herein, the term "extending the melt" means that agiven volume of melt is shaped by means which significantly increase itssurface area, such as the extension which would occur when the melt issqueezed by rollers, pressed between platens, extended between die lipsor inflated during blow molding.

In one embodiment, the polymer particles, (components (a), (b), and (c))in unmelted form are mixed thoroughly so as to provide a statisticallyhomogenous distribution. The dry mix is then fed to a single screwextruder, for example, where upon heating, the polyolefin andcompatibilizer melt first. After the higher melting ethylene-vinylalcohol copolymer subsequently melts, care must be exercised to avoidsubstantial additional mixing. The blend can also be established bycombining molten polyolefin with solid particles of ethylene-vinylalcohol copolymer and compatibilizer and then heating the combination.The success of the invention depends on establishing a meltedheterogeneous blend of polymers which, when extended, e.g. by extrusion,yields an article in which one polymer is in the form of a continuousmatrix phase and the other polymer is in the form of a discontinuousdistributed phase. The polymer comprising the discontinuous phase ispresent as a multitude of thin, parallel and overlapping layers embeddedin the continuous phase.

Although it is not required, it is preferred that both the polyolefinand the ethylene-vinyl alcohol copolymer should be mixed as particles.The particles should, as a general rule, be of a size such that themolten blend of incompatible polymers, when introduced to some meltextension means, such as extrusion die lips, exhibits the heterogeneitynecessary for practice of the invention. When the particles, especiallyparticles of the copolymer, are of too small a size, the melted blend,even though not excessively mixed, tends to function as a homogeneouscomposition because the domains of material making up the discontinuouspolymer phase are so small. When the particles, especially particles ofthe copolymer, are of too large a size, the melt blend tends to forminto shaped articles having a marbleized structure rather than a laminarstructure, the large domains of the materials which would make up thediscontinuous phase extending to opposite boundaries of the shapedarticles an causing disruption of the polyolefin which would make up thecontinuous phase. Particles about 1-7 mm, preferably about 2-4 mm on aside, are found to be particularly well suited. The particles arepreferably generally regular in shape, such as cubical or cylindrical orthe like. The particles may, however, be irregular; and they may haveone or two dimensions substantially greater than other dimension such aswould be the case, for example, when flakes of material are used.

When each of the incompatible polymers is present as individualparticles, the particles are preferably of approximately the same size,although this is not required. The compatibilizer can be provided byitself as individual particles, or it can be mixed into, coated onto, orotherwise combined with the polyolefin. It is preferred not to meltblend the compatibilizer directly with the ethylene-vinyl alcoholcopolymer prior to making the laminar articles, because thecompatibilizer appears to cause gellation or crosslinking of theethylene-vinyl alcohol copolymer when so blended. In order to insurethat the compatibilizer is well distributed in the final blend, it issometimes desirable to supply the compatibilizer in a powdered, ratherthan a pelletized form.

The thickness of the layers of material in the discontinuous phase is afunction of the particle size combined with the degree of extension inthe forming step. The particle size of the melt blend which will be thediscontinuous phase is generally selected with a view toward obtaining,after extension, overlapping layers which can be from about 0.1 to 60micrometers thick or perhaps slightly thicker.

Dry mixing particles of the polymers can be accomplished by anywell-known means such as by means of a V-blender or a tumble mixer or,on a larger scale, by means of a double-cone blender. Continuous mixingof the particles can be accomplished by any of several well-knownmethods. Of course, the particles can also be mixed by hand, the onlyrequirement of the mixing being that any two statistical samplings ofthe mixture in a given mass of material should yield substantially thesame composition. The mixing of the incompatible polymers can also beaccomplished by adding particles of the higher melting copolymer to amelt of the lower melting polyolefin maintained at a temperature belowthe higher melting point. In that case, the melt is agitated to obtainan adequate mixture; and the mixture is, thus, ready for the finalheating step.

Once mixed, the incompatible polymers are ultimately heated to atemperature greater than the melting of the higher meltingethylene-vinyl alcohol copolymer. The heating yields a moltenheterogeneous blend of materials which is ready for the stretching stepof the process. The heating must be conducted in a manner which avoidssubstantial additional mixing of the incompatible polymers because suchmixing could cause homogenization and could result in a melt and ashaped article of substantially uniform, unlayered structure. Theheating can be conducted by any of several well-known means and isusually conducted in an extruder. It has been found that a single-screwextruder of the type which is designed for material transport ratherthan material mixing can be used for the heating step and fortransporting material to the forming steps of this process withoutcausing homogenization of the molten two phase polymer composition. Lowshear and low mixing extruders of the kind normally used for polyvinylchloride, acrylonitrile, or polyvinylidene chloride can be used toprepare the articles of this invention if they are used in a way to meltand transport the materials while minimizing mixing of the components.High shear and high mixing extruders of the kind normally used for nylonand polyethylene should generally not be used.

The forming step requires extension of the molten blend followed bycooling. Melt extension can be accomplished by any of several means. Forexample, the melt can be extended by being squeezed between rollers,pressed between platens, or extruded between die lips. Molding processessuch as blow molding also cause extension in accordance with thisprocess. In the manufacture of shaped articles such as containers, theextension can be accomplished by a combination of extruding a blend ofthe heterogeneous melt to yield a container preform or parison followedby blow molding the parison into a finished container.

The extension or melt forming can be in a single direction or inperpendicular directions. Whether the forming is conducted in onedirection or two, there should be an elongation of from about 10 to 500or even 1000 percent or more in at least one direction; an elongation ofabout 100 to about 300 percent is preferred. Avoidance of excessiveextension is important only insofar as excessive elongation of the meltmay lead to weakening or rupture of the article.

Melt extension or forming is followed by cooling to below thetemperature of the melting point of the polyolefin to solidify theshaped article. The cooling can be conducted by any desired means and atany convenient rate. In the case of extension by blow molding, the moldis often chilled to cool the article; and, in the case of extruding afilm, cooling can be accomplished by exposure to cool air or by contactwith a quenching roll.

In the actual step in which extension of the melt occurs so as to formthe laminar articles of this invention, the temperature of the melt ispreferably 5°-25° C. greater than the melting point of the highermelting ethylene-vinyl alcohol copolymer. Higher temperatures lower themelt viscosities of the incompatible polymers which in turn mayfacilitate homogenization which is to be avoided.

It has been found that laminar articles prepared by extension of themolten polymer blends used in this invention generally have betterproperties if the melt viscosity of the ethylene-vinyl alcohol copolymeris somewhat greater than the melt viscosity of the polyolefin, bothviscosities being measured at about the temperature at which formingoccurs. Preferably, the melt viscosity of the ethylene-vinyl alcoholcopolymer should be from 1.1 to 3.5 times greater than the meltviscosity of the polyolefin.

EXAMPLE 1

A series of eight dry blends are prepared from particles ofpolyethylene, ethylene-vinyl alcohol copolymerand a compatibilizer bymixing in a polyethylene bag. The blends differ in that the weight ratioof compatibilizer to ethylene-vinyl alcohol copolymer (EVOH) is varied.The proportions of the ingredients in the blends are shown in Table 1-A.

                  TABLE 1-A                                                       ______________________________________                                                         EVOH     Compatibilizer                                                                          Polyethylene                              Blend            % by wt. % by wt.  % by wt.                                  ______________________________________                                        1-1              10       10.0      80.0                                      1-2              10       5.0       85.0                                      1-3              10       3.3       86.7                                      1-4              10       2.5       87.5                                      1-5    (Compar-  10       2.0       88.0                                             ative)                                                                 1-6    (Compar-  10        1.67      88.33                                           ative)                                                                 1-7    (Compar-  10       1.0       89.0                                             ative)                                                                 1-8    (Compar-  10       0.5       89.5                                             ative)                                                                 ______________________________________                                    

The EVOH used contains 30% by weight ethylene and has a melt index of3g/10 min (ASTM D-1238 Condition V) a melting point of 184° C. and amelt viscosity at 195° C. of 3022 Pa.sec at a shear rate of 30 sec⁻¹.

The polyethylene used has a density of 0.955 g/cc, a melt index of 0.35g/10 min (determined by ASTM-1238, condition E), a melting point of 134°C. and a melt viscosity at 195° C. of 2448 Pa.sec at a shear rate of 30sec⁻¹.

The compatibilizer is obtained by melt grafting maleic anhydride ontothe polyethylene described above in accordance with the teaching of U.S.Pat. No. 4,612,155. The quantity of maleic anhydride grafted onto thepolyethylene is about 1.0% by weight based on the total weight of thegrafted polymer. This concentration of maleic anhydride corresponds to acarbonyl content of about 0.57% by weight.

Laminar bottles having a capacity of about 1 L (about 1 quart) are blowmolded from each of the eight blends by feeding the dry blends to aRocheleau Model 7A continuous extrusion blow molding machine equippedwith a 2:1 compression ratio screw (diam. 38.1 mm). The bottles are blowmolded at an extrusion temperature of about 195°-200° C. All of thebottles produced exhibit a laminar distribution of the EVOH. The bottlesweigh about 62 g and have walls about 1 mm thick.

Bottles prepared from each of the blends are evaluated for (i)mechanical strength, by dropping bottles filled with water fromincreasing heights until failure, and for (ii) barrier properties, bymeasuring the loss of weight from bottles filled with xylene.

The bottle drop tests are run by filling a set of three bottles preparedfrom each of the blends with water, capping and allowing them to standat 25° C. for six days. The bottles are dropped onto smooth concretefrom increasing heights using 0.305 m (one foot) increments until thebottles fail. Ambient temperature during the testing is 17° C. Theaverage of the greatest heights passed by the three bottles in each setis shown in Table 1-B.

The effectiveness of the barrier is determined by filling a set of threebottles prepared from each of the blends with xylene, capping anddetermining the weight loss at 60° C. over a 16 day period. The bottlesare weighed periodically and their weight losses are plotted againsttime so that an average steady state weight loss can be determined foreach bottle. Based on the weight of the container and its geometry, thesurface area and average wall thickness are calculated (ASTM - 2684).Permeability values (P) are then calculated. The average of the valuesobtained for each set of bottles is also shown in Table 1-B.

The ratio of the weight of carbonyl groups furnished by thecompatibilizer to the weight of EVOH is also given for each of theblends in Table 1-B.

                  TABLE 1-B                                                       ______________________________________                                                                            Permeability                                               Ratio      Drop Test                                                                             g · mm/                          Blend.           CO/EVOH.sup.1                                                                            m (ft)  day · m.sup.2                    ______________________________________                                        1-1              0.0057      3.4 (11)                                                                             3.8                                       1-2              .0029      2.1 (7) 6.0                                       1-3              .0019      2.1 (7) 5.7                                       1-4              .0014      2.1 (7) 5.4                                       1-5    (Compar-  .0011      1.8 (6) 6.9                                              ative)                                                                 1-6    (Compar-  .0010      0.9 (3) 7.0                                              ative)                                                                 1-7    (Compar-  .0006      1.8 (6) 12.8                                             ative)                                                                 1-8    (Compar-  .0003      0.9 (3) 14.3                                             ative)                                                                 ______________________________________                                         .sup.1 defined in specification                                          

Bottles prepared from blends 1--1 to 1-4 which are within the scope ofthis invention exhibit good mechanical strength as evidenced by the droptest results and a low permeability to xylene at 60° C. Bottles preparedfrom comparative blends 1-5 to 1-8 are beyond the scope of thisinvention and exhibit lower mechanical strength with greater variationsand increasing degrees of permeation.

Example 12 of European Patent Application 15556 describes a laminar filmprepared from a blend of 30 parts EVOH, 5 parts of a compatibilizerderived by grafting 0.9% by weight of fumaric acid onto polyethylene and65 parts of polyethylene. The weight ratio of carbonyl content to EVOHin Example 12 of the European Patent Application is 0.00072. This valuefalls between the ratios for comparative blends 1-6 and 1-7. Theseblends yield bottles which are inferior to those prepared fromcompositions within the scope of the invention.

It is recognized that Example 12 of the European Patent Application usesEVOH at a 30% by weight level while the blends in this Example contain10% by weight of EVOH. In order to make a more direct comparison withthe composition of Example 12 of European Patent Application 15556, twocompositions are prepared from the same ingredients used hereinbefore inthis Example but in the amounts shown in Table 1-C.

                  TABLE 1-C                                                       ______________________________________                                                 EVOH       Compatibilizer                                                                            Polyethylene                                  Blend    % by wt.   % by wt.    % by wt.                                      ______________________________________                                         1-9 (Comp)                                                                            30         5           65                                            1-10 (Comp)                                                                            30         3           67                                            ______________________________________                                    

Bottles are prepared as before and tested by dropping and towardpermeation to xylene. The results as well as the weight ratio ofcarbonyl to EVOH are given in Table 1-D.

                  TABLE 1-D                                                       ______________________________________                                                              Drop Test Permeability                                  Blend    Ratio CO/EVOH                                                                              m (ft)    g · mm/day · m.sup.2        ______________________________________                                         1-9 (Comp)                                                                            0.0010       0.9 (3)   0.34                                          1-10 (Comp)                                                                            0.0006       0.6 (2)   2.55                                          ______________________________________                                    

The ratios for these Comparative tests bracket the carbonyl/EVOH ratioof 0.00072 for Example 12 of the European Patent Application. Clearlythe bottles prepared from comparative blends 1-9 and 1-10 are inferiorin mechanical strength compared with the bottles prepared from blendswithin the scope of this invention. The permeability values are lowerfor these comparisons because the amount of EVOH is triple that used inruns 1--1 to 1-4; however, the permeability does show a large variation.

EXAMPLE 2

A number of compatibilizers are tested for their ability to adhere EVOHto polyethylene or polypropylene in laminar films. Each of thecompatibilizers contains either grafted or copolymerized maleicanhydride moieties. The compatibilizers are as follows:

A. 1% by weight maleic anhydride grafted to polyethylene.

B. 2% by weight maleic anhydride grafted to an ethylene/propylene/dienerubber containing about 4% by weight of units derived from1,4-hexadiene.

C. 1.5% by weight maleic anhydride grafted to an ethylene-vinyl acetatecopolymer containing 9% by weight vinyl acetate.

D. 1.06% by weight maleic anhydride grafted to an ethylene-vinyl acetatecopolymer containing 28% by weight vinyl acetate.

E. 5.5% by weight of copolymerized maleic anhydride in a maleicanhydride/styrene copolymer.

F. 10% by weight of copolymerized maleic anhydride in a maleicanhydride/styrene copolymer.

G. 3.6% by weight of maleic anhydride grafted to polypropylene.

The dry blends shown in Table 2-A are prepared from the abovecompatibilizers and the polyethylene and EVOH copolymer used in Example1.

                  TABLE 2-A                                                       ______________________________________                                               EVOH  Polyethylene Compatibilizer                                      Blend    g       g            Type  g                                         ______________________________________                                        1-1       0      2000         --     0                                        2-2      200     1700         A     100                                       2-3      200     1750         B     50                                        2-4      200       1737.4     C       66.6                                    2-5      200     1700         D     100                                       2-6      200     1780         E     20                                        2-7      200     1790         F     10                                        2-8      200     1772         G     28                                        ______________________________________                                    

Laminar films 0.5 mm (20 mils) thick are prepared from each of theblends using a Wayne "Yellow Jacket" 25.4 mm (1 inch) extruder with astandard screw feeding a Wayne 152 mm (6 inch) sheet die at a dietemperature of 190° C. The laminar films are tested for adhesion of theEVOH layers with the polyethylene by flexing samples of film 180° (thefilms are actually creased as one would fold a piece of paper) indifferent directions (machine direction, transverse direction anddiagonally) and checking for delamination. The films are rated from 1 to5 according to their resistance to delamination, with 5 being excellentand showing no signs of delamination down to 1 being poor and showingessentially no resistance to delamination. The results of these flexingtests are presented in Table 2-B. The weight ratio of carbonyl contentfurnished by the compatibilizer to EVOH is also given in Table 2-B foreach of the blends.

                  TABLE 2-B                                                       ______________________________________                                                                        Resistance                                    Blend Compatibilizer                                                                             Ratio CO/EVOH                                                                              to Delamination                               ______________________________________                                        2-1   --           --           5                                             2-2   A            0.0029       5                                             2-3   B            0.0029       1                                             2-4   C            0.0028       3                                             2-5   D            0.0030       3                                             2-6   E            0.0031       1                                             2-7   F            0.0029       2                                             2-8   G            0.0029       3-4                                           ______________________________________                                    

Blend No. 1 is pure polyethylene which was run as a control. Blend No. 2which is within the scope of this invention in that it employs acompatibilizer based on polyethylene which corresponds to the matrixpolymer yields films which do not exhibit any sign of delamination. Allof the other blends yield films which show obvious delamination. This issurprising particularly for films derived from Blend Nos. 3 and 8 whichuse compatibilizers based on polyolefin backbones which while notsoluble in the polyethylene matrix polymer are similar in many respectsto the matrix polymer.

A second series of blends is prepared in which polypropylene serves asthe matrix resin. The polypropylene used has a melt index of 3-4 g/10min. (determined by ASTM - 1238, condition L), a melting point of 168°C. and a melt viscosity at 195° C. of 1458 Pa.sec at a shear rate of 30sec⁻¹ The EVOH copolymer is the same as that used in Example 1. Thecompatibilizers are those previously described in this example. Thecompositions of these blends is given in Table 2-C.

                  TABLE 2-C                                                       ______________________________________                                                                    Compatibilizer                                    Blend  EVOH, g   Polypropylene, g                                                                             Type  g                                       ______________________________________                                        2-9     0        2000           --     0                                      2-10   200       1770           G     30                                      2-11   200       1728           C     72                                      2-12   200       1746           B     54                                      2-13   200         1780.4       E       19.6                                  2-14   200         1789.2       F       10.8                                  2-15   200       1692           A     108                                     ______________________________________                                    

Laminated films 0.5 mm (20 mils) thick are prepared from the blendsusing the Wayne extruder previously described but with a die temperatureof 195° C. The films are rated as described before by creasing. Theresults are presented in Table 2-D.

                  TABLE 2-D                                                       ______________________________________                                                                        Resistance                                    Blend Compatibilizer                                                                             Ratio CO/EVOH                                                                              to Delamination                               ______________________________________                                        2-9   --           --           5                                             2-10  G            0.0031       4.5-5                                         2-11  C            0.0031       1                                             2-12  D            0.0031       1                                             2-13  B            0.0031       1                                             2-14  E            0.0031       1                                             2-15  F            0.0031       1                                             2-16  A            0.0031       2                                             ______________________________________                                    

Blend No. 2-9 is pure polypropylene which is run as a control. OnlyBlend No. 10 which employs a compatibilizer based on polypropylene whichmatches the matrix polymer exhibits acceptable adhesion. The rating of4.5-5.0 for Blend No. 10 indicates that some of the flex tests showed nosign of delamination while other tests showed only slight signs ofdelamination such as some hazing of the polymer film where it wascreased. Surprisingly, compatibilizers A and B which are maleicanhydride grafts to polyolefin backbones other than polypropyleneprovide little adhesion.

EXAMPLE 3

This example illustrates the effect of compatibilizer concentration onthe adhesion observed for laminar blow molded bottles prepared from EVOHand polypropylene. The compatibilizer used is compatibilizer G ofExample 2, supplied in the form of a granulate with particle size about0.86 mm (about 20 mesh). The EVOH copolymer used is described inExample 1. Three different commercial samples of polypropylene are usedand are described as follows:

A. A polypropylene homopolymer having a melt index of 4 g/10 min. soldby Shell as 5A44.

B. A polypropylene homopolymer having a melt index of about 3 g/10 min.sold by Himont as PD-064.

C. A polypropylene homopolymer having a melt index of 2.2 g/10 min. soldby Shell as 5384.

Two different blow molding machines are used in making the bottlesdescribed hereinafter. One is the Rocheleau Model 7A continuousextrusion blow molding machine, hereinafter R, described in Example 1.This machine is used to prepare 1 liter bottles and is operated at ascrew speed of 80 rpm. The other machine is a Hayssen continuous blowmolding machine, hereinafter H, which is used to make 1 liter bottlesand is operated at a screw speed of 50 rpm.

Table 3-A describes a number of bottles prepared under the conditionsindicated from dry blends containing 10% by weight EVOH, amounts ofcompatibilizer as shown in the Table, with the balance beingpolypropylene as indicated.

The adhesion results are reported on a scale of 5 (excellent) to 1(poor). The adhesion is judged by observing the extent of delaminationresulting from (A) squeezing a bottle on opposite sides of the verticalmidpoints of its cylindrical body until the interior surfaces of thecylindrical walls meet and (B) indenting the shoulder of a bottle withone's thumb, the shoulder being that portion of a bottle where itscylindrical body joins its conical portion connecting its cylindricalbody to its neck. (The stresses resulting from indenting the shoulderare much greater than those induced by squeezing the body of thebottle.) Bottles which exhibit no signs of delamination at the shoulderor in the middle are rated 5. Bottles showing some delamination at theshoulder, but none in the middle, rate 4. Bottles showing traces ofdelamination in the middle, rate 3. Bottles showing some spreading ofdelamination from where they are squeezed in the middle, rate 2. Forbottles in which the delamination spreads from top to bottom uponsqueezing, the rating is 1.

                                      TABLE 3A                                    __________________________________________________________________________    Bottle                                                                            Compat.                                                                            Polyprop.                                                                           Molding                                                                            Extrudate                                                                           CO/EVOH                                                                             Adhesion                                      No. wt % Type  Machine                                                                            Temp., °C.                                                                   Ratio Rating                                        __________________________________________________________________________    3-1 5.0  A     R    196   0.0103                                                                              5.0                                           3-2 1.0  A     R    196   0.00206                                                                             4.5                                           3-3 0.5  A     R    193   0.00103                                                                             4.8                                           3-4 1.0  B     R    200   0.00206                                                                             4.0                                           3-5 0.5  B     R    197   0.00103                                                                             3.9                                           3-6 1.0  A     R    205   0.00206                                                                             5.0                                           3-7 1.0  C     R    205   0.00206                                                                             4.5                                           3-8 0.5  C     R    203   0.00103                                                                             4.0                                           3-9 0.5  C     R    207   0.00103                                                                             4.0                                            3-10                                                                             0.5  C     R    210   0.00103                                                                             3.5                                            3-11                                                                             0.5  C     R    213   0.00103                                                                             3.5                                            3-12                                                                             1.0  C     H    202   0.00206                                                                             5.0                                            3-13                                                                             1.0  C     H    206   0.00206                                                                             4.5                                            3-14                                                                             1.0  C     H    210   0.00206                                                                             4.5                                            3-15                                                                              0.75                                                                              C     H    203   0.00155                                                                             2.5                                            3-16                                                                             0.5  C     H    204   0.00103                                                                             1.5                                           __________________________________________________________________________

Bottle numbers 3, 5, 8, 9, 10, 11 and 16 are all prepared with 0.5 wt. %compatibilizer, which corresponds to CO/EVOH ratio of 0.00103, below thelower limit of 0.0014. The adhesion ratings for these seven bottlesaverage 3.6. Bottle numbers 2, 4, 6, 7, 12, 13 and 14 are all preparedwith 1.0 wt. % compatibilizer, which corresponds to a CO/EVOH ratio of0.00207, above the lower limit of 0.0014. The adhesion ratings for theseseven bottles average 4.6. Bottle 15 is a borderline example.

While some of the bottles prepared with 0.5 wt. % compatibilizer havegood or excellent adhesion, they exhibit greater variation in adhesionthan do bottles prepared with 1.0 wt. % compatibilizer, which uniformlyexhibit very good to excellent adhesion. At 0.5 wt. % compatibilizer,adhesion seems to be much more sensitive to changes in materials orprocessing conditions.

EXAMPLE 4

Film samples are prepared from a random copolymer of propylene and about1.5 mole % ethylene, melt index 2.1 g/10 min, m.p. 155° C., anethylene-vinyl alcohol copolymer containing 29 mole % ethylene, and as acompatibilizer, Admer™ QF 500, a product of Mitsui PetrochemicalCompany. It is believed that Admer™ QF 500 is a melt blend of maleicanhydride grafted polypropylene, linear low density polyethylene, andungrafted polypropylene. The proportions of these components are notknown, nor is it known whether any additional ingredients are present.Analysis by titration indicates that Admer™ QF 500 contains 0.12±0.02%by weight anhydride (measured as maleic anhydride), which corresponds toa carbonyl content of about 0.068% by weight.

The film samples contain 10% EVOH, Admer™ QF 500 in the amountsindicated in Table 4, and the remainder polypropylene. They are preparedby dry blending component particles in a polyethylene bag, followed byextrusion of 0.5 mm (20 mil) films as in Example 2, at the temperatureindicated. The oxygen permeation values, in units of cm³ -mm/day-m² -atmare measured and are reported in Table 4.

                  TABLE 4                                                         ______________________________________                                        Blend % Admer ™                                                                             Ratio CO/EVOH                                                                              Die temp., °C.                                                                   OPV                                   ______________________________________                                        4-A   10         0.0068       195       1.74                                                                210       2.82                                  4-B   15         0.0102       195       2.68                                                                210       2.31                                  4-C   20         0.0136       195       2.22                                                                210       5.22                                  4-D   25         0.0171       195       1.78                                                                210       8.68                                  ______________________________________                                    

Samples A, B, and C are at or below the lower limit of 0.0014 for theCO/EVOH ratio. Sample D is slightly above this limit, but below thepreferred lower limit of 0.002. The adhesion of all eight of these filmsis poor, based on the ease with which they delaminate when flexed.Samples C and D (extruded at 210°) exhibit slightly improved adhesion.The cause of the poor adhesion of Sample D, which is a borderlineexample, is not definitely known, but may arise from the presence of oneor more unidentified components in the Admer™ QF 500 which may becomeimportant, particularly at unusually high concentrations of the Admer™.It has been found, for example, that the presence of antiadhesivecompounds can lead to erratic results. Deleterious materials should, ofcourse, be avoided. Furthermore, rheological properties of the Admer™may lead to deleterious effects when the Admer™ itself becomes a majorcomponent of the blend. Finally, the mixing performance of the smallextruder used in this example may be inferior to that of a largerextruder. Thus under different processing conditions, better resultsmight have been attained for Sample D.

I claim:
 1. A process for manufacturing a laminar, shaped article ofpolymeric material comprising the steps of:(a) establishing a melted,heterogeneous blend of polyolefin, an ethylene-vinyl alcohol copolymercontaining about 20-60% by weight of ethylene units and having a meltingpoint at least about 5° C. higher than the polyolefin, and acompatibilizer comprising a polyolefin backbone having grafted thereoncyclic anhydride moieties, in an amount such that the carbonyl contentof the compatibilizer is about 0.3-4.0% by weight, said polyolefinbackbone prior to grafting being miscible with said polyolefin, thequantity of said compatibilizer in the blend being such that the ratioof the weight of carbonyl groups to the weight of the ethylenevinylalcohol copolymer is about 0.0014:1 to about 0.006:1; (b) extending abody of the melt; and (c) cooling the extended body to below the meltingpoint of the polyolefin.
 2. The process of claim 1 wherein the melted,heterogeneous blend is established by heating particles of a combinationof the polyolefin and the compatibilizer and particles of theethylene-vinyl alcohol copolymer, without substantial additional mixing,to a temperature above the melting point of the ethylene-vinyl alcoholcopolymer.
 3. The process of claim 1 wherein the melted heterogeneousblend is established by heating particles of the polyolefin withparticles of a combination of the compatibilizer and the ethylene-vinylalcohol copolymer, without substantial additional mixing, to atemperature above the melting point of the ethylene-vinyl alcoholcopolymer.
 4. The process of claim 1 wherein the polyolefin is selectedfrom the group consisting of polyethylene, polypropylene, andpolybutylene homopolymers and copolymers.
 5. The process of claim 4wherein the polyolefin is selected from the group consisting ofpolyethylene and polypropylene.
 6. The process of claim 5 wherein thepolyolefin is polyethylene.
 7. The process of claim 1 wherein theethylene-vinyl alcohol copolymer is at least about 95% saponified. 8.The process of claim 7 wherein the ethylene-vinyl alcohol copolymer isat least about 99% saponified.
 9. The process of claim 1 wherein theethylene-vinyl alcohol copolymer has a melting point of at least about10° C. greater than that of the polyolefin.
 10. The process of claim 1wherein the compatibilizer is a polyolefin backbone having graftedthereon moieties derived from maleic anhydride.
 11. The process of claim1 wherein the carbonyl content of the compatibilizer is about 0.3-3.0%by weight.
 12. The process of claim 1 wherein the carbonyl content ofthe compatibilizer is about 0.5-2.5% by weight.
 13. The process of claimwherein the polyolefin backbone of the compatibilizer is substantiallythe same as the first-named polyolefin component.
 14. The process ofclaim 1 wherein the quantity of compatibilizer is such that the ratio ofthe weight of carbonyl groups to the weight of ethylene-vinyl alcoholcopolymer is about 0.002:1.0 to about 0.004:1.0.
 15. The process ofclaim 1 wherein the quantity of polyolefin is at least about 60%. 16.The process of claim 15 wherein the quantity of polyolefin is at leastabout 70%.
 17. The process of claim 1 wherein the quantity of polyolefinis about 80 to about 90%, the quantity of ethylene-vinyl alcoholcopolymer is about 5 to about 15%, and the amount of the compatibilizeris about 0.5 to about 10%.
 18. The process of claim 1 wherein thearticle formed thereby contains the ethylene-vinyl alcohol copolymer inthe form of thin, substantially parallel, overlapping layers ofmaterial.